Abstract
An in vitro model was developed to assess the effects of topical antimicrobials on taxonomically defined wound biofilms. Biofilms were exposed over seven days to povidone-iodine, silver acetate or polyhexamethylene biguanide (PHMB) at concentrations used in wound dressings. The rank order of tolerance in multi-species biofilms, based on an analysis of the average bacterial counts over time was P. aeruginosa > methicillin-resistant Staphylococcus aureus (MRSA) > B. fragilis > S. pyogenes. The rank order of effectiveness for the antimicrobials in the biofilm model was povidone-iodine > PHMB > silver acetate. None of the test compounds eradicated P. aeruginosa or MRSA from the biofilms although all compounds except silver acetate eliminated S. pyogenes. Antimicrobial effectiveness against bacteria grown in multi-species biofilms did not correlate with planktonic susceptibility. Defined biofilm populations of mixed-species wound pathogens could be maintained in the basal perfusion model, facilitating the efficacy testing of treatments regimens and potential dressings against multi-species biofilms composed of wound isolates.
Highlights
Chronic wounds represent a considerable challenge to wound care professionals and healthcare resources, having a significant bearing upon patient morbidity and mortality (Scali and Kunimoto2013)
Whilst the processes influencing the transition to a chronic wound state are complex and depend on host factors such as wound aetiology, co-morbidities and anatomical location, infection and the presence of biofilms have been implicated as important contributors (Roy et al 2014, Scali and Kunimoto 2013, Schierle et al 2009)
The association of biofilms with chronic wounds (Bjarnsholt et al 2008, Kanno et al 2009, Neut et al 2011, Roy et al 2014, Wolcott and Rhoads 2008) has driven the development and application of antimicrobial dressings based on their effectiveness against the most recalcitrant forms of microbial growth present in this environment, which includes organisms displaying biochemical resistance, such as Pseudomonas spp. (Ramos et al 2010, Rochex and Lebeault 2007, Walters et al 2003), Methicillin resistant Staphylococcus aureus (MRSA) (McCarthy et al 2015, Ohadian Moghadam et al 2014) and microbial biofilms, that generally exhibit greater tolerance to antimicrobials than their planktonic counterparts regardless of taxonomic composition (Gilbert et al 2002)
Summary
Chronic wounds represent a considerable challenge to wound care professionals and healthcare resources, having a significant bearing upon patient morbidity and mortality (Scali and Kunimoto2013). Whilst the processes influencing the transition to a chronic wound state are complex and depend on host factors such as wound aetiology, co-morbidities and anatomical location, infection and the presence of biofilms have been implicated as important contributors (Roy et al 2014, Scali and Kunimoto 2013, Schierle et al 2009). (Ramos et al 2010, Rochex and Lebeault 2007, Walters et al 2003), Methicillin resistant Staphylococcus aureus (MRSA) (McCarthy et al 2015, Ohadian Moghadam et al 2014) and microbial biofilms, that generally exhibit greater tolerance to antimicrobials than their planktonic counterparts regardless of taxonomic composition (Gilbert et al 2002) The association of biofilms with chronic wounds (Bjarnsholt et al 2008, Kanno et al 2009, Neut et al 2011, Roy et al 2014, Wolcott and Rhoads 2008) has driven the development and application of antimicrobial dressings based on their effectiveness against the most recalcitrant forms of microbial growth present in this environment, which includes organisms displaying biochemical resistance, such as Pseudomonas spp. (Ramos et al 2010, Rochex and Lebeault 2007, Walters et al 2003), Methicillin resistant Staphylococcus aureus (MRSA) (McCarthy et al 2015, Ohadian Moghadam et al 2014) and microbial biofilms, that generally exhibit greater tolerance to antimicrobials than their planktonic counterparts regardless of taxonomic composition (Gilbert et al 2002)
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